The System Architecture Evolution (SAE) is the core network architecture of the Third Generation Partnership Project's (3GPP) Long Term Evolution (LTE) wireless communication standard. SAE is the evolution of the General Packet Radio service (GPRS) Core Network, with some differences including a simplified architecture, the fact that it is based on an all IP Network (AIPN), has support for higher throughput and for lower latency access networks (e.g. Radio Access Networks, RANs) and for mobility between multiple heterogeneous RANs, including legacy systems as GPRS, but also non-3GPP systems (e.g. WiMAX). The main component of the SAE architecture is the Evolved Packet Core (EPC), also known as the SAE Core. The EPC serves as equivalent of the GPRS networks (via the Mobility Management Entity, Serving Gateway and Packet Data Gateway (PGW) subcomponents). In the EPC, the PGW provides connectivity from the User Equipment (UE) to external packet data networks by being the point of exit and entry of data traffic for the UE. A UE may have simultaneous connectivity with more than one PGW for accessing multiple Packet Data Networks (PDNs). The PGW also performs policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screening. Finally, another key role of the PGW is to act as the anchor for mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA 1X and EvDO).
Reference is now made to FIG. 1.a which is a simplified prior art representation of a 3GPP-based telecommunications network. Shown in FIG. 1.a is a UE 101 connected via a radio network 103 to a serving gateway 105 and a PDN gateway 107. The PDN gateway acts to connect the UE 101 to IP networks and services 113. The radio network 103 may include an E-UTRAN (evolved UMTS Terrestrial Radio Access Network) or any other type of radio network. Together, the serving gateway 105 and the PDN gateway 107 form a gateway functionality 109 that insures packet data connection for the UE 101 with the IP networks 113.
In the EPC, the S5 interface reference point (also called S5 herein) provides user plane tunnelling and tunnel management between Serving GW 105 and the PDN GW 107. It is used for Serving GW 105 relocation due to UE mobility and if the Serving GW 105 needs to connect to a non-collocated PDN GW 107 for the required PDN connectivity. S5 is based on GTP protocol. The PMIP variant of S5 is described in 3GPP's Technical Specification TS 23.402, all of which is herein incorporated by reference.
The EPC's S8 inter-PLMN interface reference point (not shown in FIG. 1.a) provides user and control plane between the Serving GW in a Visited-PLMN and the PDN GW in a Home-PLMN. S8 is the inter PLMN variant of S5. S8 is based on GTP protocol. The PMIP variant of S8 is described in the same 3GPP TS 23.402 referred to hereinbefore.
When a UE attaches into a 3GPP based radio access network, it may set up one or more PDN connections with a network. Each such PDN connection can have a different PDN type, including, for example Internet Protocol (IP) version 4 (IPv4) only, IPv6 only or IPv4/IPv6. With IPv6 only or IPv4/IPv6 PDN type, the UE is assigned an IPv6 network prefix via IPv6 stateless address auto-configuration. The IPv6 network prefix can be assigned in various ways.
For example, in S5/S8 PMIPv6, the IPv6 network prefix is assigned by the PDN Gateway (PDN GW) and returned to the Serving Gateway in a Proxy Binding Acknowledgement message. The Serving GW then sends a router advertisement message with the allocated IPv6 prefix to the UE once the PDN connection is established, so that the UE can use the prefix in order to configure its IPv6 address. On the other hand, in S5/S8 GTPv2 (General Packet Radio Service Tunnelling Protocol version 2), the IPv6 network prefix is assigned by the PDN GW and sent directly to the UE in a router advertisement message once the PDN connection is established without involving the Serving Gateway. Like before, upon receiving the router advertisement message, the UE configures its globally unique IPv6 address.
In the current 3GPP based implementation, it is assumed that a network always sends an IPv6 router advertisement message upon receiving the routing solicitation message from the UE, or at any time after the PDN connection is setup including at initial attachment, during an access handover with the Serving GW relocation, or during a handover from none 3GPPIP access to 3GPP access. After the PDN connection is setup, the network also renews the IPv6 prefix periodically. For this purpose, the Serving GW sends an IPv6 router advertisement message to the UE with the same IPv6 prefix and new non-zero values in preferred and valid lifetime fields, before the expiry of the router lifetime or prefix lifetime.
For example, according to the current 3GPP implementations, there is a lifetime of the IPv6 router advertisement message. When the lifetime timer expires, the UE has to remove the prefix from its routing table which renders the UE unable to send any uplink packets for a certain duration. In order to maintain its routing table usable, the UE has to renew its IPv6 address, and for this purpose sends a Router Solicitation message to the network asking for an IPv6 prefix extension. Alternatively, the PDN GW or the Serving GW needs to periodically send to the UE an IPv6 router advertisement message, solicited or not, in order to avoid the lifetime expiration and the misconfiguration of the UE's IPv6 address. Also during mobility procedures involving the UE, such as for example in the context of an inter-Mobility Access Gateway (MAG) handover, the target Serving GW does not necessarily know when the router advertisement lifetime expires. Therefore, the target Serving GW must send an IPv6 router advertisement to the UE every time a handover is completed.
There is a belief in the industry that the extra paging generated by IPv6 router advertisement messages sent when the UE is in idle mode does not cause any concern because IPv6 router advertisement messages are considered necessary UE signalling messages. According to these beliefs, such router advertisement messages need to be sent to the UE periodically in order to always keep the UE routing table correct. However, it was recently noted that some issues can occur and that the periodic transmission of router advertisement messages are not without creating adverse effects.
For example, the 3GPP UE may be in an idle mode, i.e. with no network connection established over the air interface, when an IPv6 router advertisement message is sent by the PDN GW to the Serving GW. Sending an IPv6 router advertisement message to an idle mode UE triggers the network to page that UE, which results in the UE establishing a user plane connection that wakes up the UE from idle mode, in order to allow i) for the UE to receive the IPv6 prefix, and ii) for the UE's routing table to be updated according to the received prefix. The above procedure results in a lot of network signalling which is totally unnecessary when the UE is in idle mode, since when in such a mode, the UE does not exchange any data with the network. Moreover, to wake up an idle mode UE too often also results in the faster depletion of the UE's battery.
Reference is now made to FIG. 1.b (prior art) that shows an exemplary flow-chart diagram illustrative of the current prior art implementation of the transmission of a router advertisement message towards a UE that is in idle mode. In action 102, a PDN GW receives downlink data destined to a UE, such as for example a router advertisement message. In action 104, it is detected whether or not the UE is in idle mode, and if not, i.e. if the UE is being detected to be in active mode with a radio interface connection already established with the network, in action 106 the downlink data is transmitted to the UE, including for example the router advertisement message. In action 108, the UE receives and processes the router advertisement message and configures its own IPv6 address using the IPv6 Network Prefix. However, if in action 104, it is rather detected that the UE is in idle mode, i.e. with no radio interface connection established with the network, the GW pages the UE in action 110 in order to cause the UE to transition from the idle mode to active mode in action 112, so that the downlink data including the router advertisement message can be transmitted from the GW into the UE, in action 114. In action 116, the UE receives the data including the router advertisement message, and configures its own IPv6 address using the IP prefix included with the router advertisement message. In action 118, provided that the UE has no other data to exchange with the network, the UE may go back to idle mode and terminate the radio interface connection with the network.
Waking-up a UE from idle mode for the simple purpose of sending the router advertisement message causes the UE to deplete its internal battery faster, which can have negative consequences on the subsequent communications of the UE with the network. Likewise, the actions performed by both the UE and the network for the mere purpose of configuring a new IP address for the UE involves additional signalling between the UE and the network that causes sometimes unnecessary load on the network. For example, in many instances, a UE could be kept in idle mode for extended periods of time had it not been for the receipt of the router advertisement messages. Other times, configuring a new IP address may prove useless, since the UE may never make actual use of such a configuration if the UE is kept in idle mode until the next router advertisement message is received.
Although there is no prior art solution as the one proposed hereinafter for solving the above-mentioned deficiencies, the U.S. Pat. No. 7,881,322 bears some relation with the field of the present invention. In this patent, there is disclosed a power-saving mechanism for establishing periodic traffic streams in wireless local area networks. According to the U.S. Pat. No. 7,881,322, a method for coordinating the delivery and receipt of frames from a power-saving station in a wireless local area network is disclosed. According to that patent, a wake-up schedule is established for power-saving stations based on a temporal period and temporal offset that reduces the frequency with which multiple stations in a network wake-up simultaneously, thereby reducing traffic delays and power consumption. In more particular, according to the U.S. Pat. No. 7,881,322, a station, prior to entering power-saved mode, sends a request to an access point that specifies a desire scheduled period for subsequent wake-up that is independent of beacons. The access point determines, based on existing poling and wake-up schedules, a temporal offset that reduces the occurrence of concurring wake-ups of other stations, and sends a positive notice of the temporal offset to the station.
The US patent application publication US 2008/0233905A1 also bears some relation with the field of the present invention. Therein, there is provided a subscriber station in sleep mode that is capable of sending and receiving traffic during sleep mode without violating the delay requirements or best effort traffic. Moreover, the subscriber station is capable of remaining asleep and may optionally only be awaken in the event there is data to be transmitted from the base station to the subscriber station or from the subscriber station to the base station. By implementing the wake-up arrangement, the power consumption of the subscriber station can be reduced.
However, none of the above-mentioned implementations provides a solution as the ones specified in the present invention.
Accordingly, it should be readily appreciated that in order to overcome the deficiencies and shortcomings of the existing solutions, it would be advantageous to have a method and system for efficiently handling the delivery of router advertisement messages to the UE. The present invention provides such a method and system.